1. Field of the Invention
The present invention relates to a traveling vehicle system. In particular, the present invention relates to detection of obstacles.
2. Description of the Related Art
In a known technique, as an obstacle sensor, a distance sensor such as a laser distance meter is used. A monitor area, e.g., having a sector shape is scanned by the distance sensor, and a distance and an orientation relative to an obstacle are determined. Obstacles detected by the obstacle sensor do not always interfere with the traveling vehicle, and some of the detected obstacles may not interfere with the traveling vehicle. It is because the obstacle sensor detects obstacles over a wide range of angles. For example, the obstacle sensor detects obstacles that are positioned on a side of a travel route of the traveling vehicle, and do not interfere with the traveling vehicle.
In this respect, JP2002-215238A proposes to store a plurality of patterns of detection areas, and select a pattern of the detection area in correspondence with the position of a traveling vehicle. Among obstacles detected by an obstacle sensor, only obstacles within the detection area are determined as actual obstacles. However, it is difficult to store a large number of patterns of detection areas. Therefore, optimum patterns may not always be available. For the sake of safety, excessively wide detection areas may be used. As a result, the distance to the leading traveling vehicle becomes excessively large. Further, in practice, obstacles that do not interfere with the traveling vehicles are detected as well. In order to avoid collision with such obstacles, unwanted deceleration control or the like may be implemented. Therefore, the efficiency in the traveling vehicle system becomes low. If the detection area is narrowed to give a priority to the efficiency, dead angles where the obstacles cannot be detected may exist undesirably.